Modern farming continues to make significant strides in the industry's ability to produce larger and more robust foods in response to demand and increasing populations. For example, advances in chemical engineering, fertilization, irrigation, soil analysis and equipment (hardware and software) have revolutionized crop production and associated systems. In this evolution of farming techniques, modern farming has increasingly turned to technological advances in the full stream of farming such as planting, tending and harvesting of crops which requires a wide range of tools, equipment, machinery, chemicals and other materials.
For example, vehicle mounted spraying systems incorporating a boom that extends laterally on both sides of a vehicle such as a tractor are commonly used to spray agricultural crops with liquid based products such as fertilizers or other chemicals. Typically, these types of spraying systems are mounted to the rear of the vehicle which will also carry a tank containing the liquid that is to be sprayed. To ensure that the correct amount of liquid is sprayed, the spraying system is configured so that a given flow rate is dispensed from a plurality of sprayers located along the arm at a predetermined height above the surface to be sprayed. Often these vehicle mounted spraying systems will incorporate a height adjustment capability to allow the overall height of the boom to be adjusted as desired. Booms vary in size, with typical wing tip to wing tip lengths of 90 feet, 120 feet and 150 feet.
Such spraying systems prove very adequate over flat terrain, however, where the surface to be sprayed is undulating or sloped simple height adjustment of the boom relative to the vehicle is not sufficient as the ground to the right of the vehicle may be elevated with respect the ground surface to the left of the vehicle. To overcome this problem, the boom is commonly divided into separate articulated arms or wings each of which are independently adjustable by hydraulic rams which function to raise or lower the booms in accordance with a control signal provided by ultrasonic distance sensors located on each wing. These distance sensors measure the distance between the wing and the ground surface. In this manner, either the left or right wing of the boom may be automatically raised or lowered as required.
However, there are a number of disadvantages with this approach. As the wings extend for relatively large distances from the vehicle, the wings are mounted to a central rigid support structure which itself is resiliently mounted to the vehicle. This resilient mounting includes a combination of springs, shock absorbers and pendulums so as to absorb severe twisting and movement shocks and provide some mechanical self levelling of the boom. This mounting also provides approximately ±10° of travel in the roll direction which functions to absorb the significant stresses that the central support structure would otherwise encounter if it were to be rigidly mounted to the vehicle.
Unfortunately, the effect of this resilient mounting is to greatly reduce the stability of the wing height control as, for example, raising the left wing to compensate for a raised ground profile in this region will in fact cause the right wing to pivot upwardly due to the torque imparted on the entire boom by the redistribution of weight on the left hand side. This will then result in a control signal being sent to the right hand side to lower the right wing, thereby leading to a potential instability. Eventually, the boom will reach equilibrium but only after a delay of approximately one to three seconds during which time the sprayed liquid will not be dispensed in the correct amounts over the ground.
Another significant disadvantage of existing vehicle mounted spray systems occurs when the vehicle encounters a local undulation in the surface such as a rock or a rut in the ground that causes the vehicle to rapidly change lateral slope angle. In extreme circumstances, this could cause the tip of a wing to impact the ground as the speed of response of the ultrasonic distance sensors located on the wings is not rapid enough to prevent this from occurring. Even in the case where an impact is avoided, the raising of the wing to avoid the impact will cause the raising of the opposed wing as discussed earlier, once again resulting in a certain instability of the spraying system.
As highlighted above, the terrain over which such sprayers systems operate can heavily impact the overall stability of the sprayer and the performance of the sprayer in terms of dispensing the specific liquid (e.g., fertilizer) at the desired rate and coverage area. In the field of precision agriculture, agricultural drones and/or so-called unmanned aerial vehicles (UAV) exist that are used to study terrains and have been used to capture highly accurate images of fields and crops that cover hundreds of hectares/acres in a single flight. Such image data is combined with available post-flight data/image processing software to transform the captured images into, for example, one or more orthomosaic images and/or digital elevation models, generate custom vegetation indices to detect structural, chlorophyll and water stresses and/or evaluate irrigation management. For example, the images and other information collected by such agricultural drones can be analyzed on a post-flight basis using available image processing and data processing software that will provide normalized differential vegetation index (NDVI) maps, 2D index maps, 2D geo-referenced orthomosaics, 3D textured mesh, 3D digital surface models (DSM), contour lines, application maps, thermal field maps, reflectance maps and other crop monitoring/analysis. For example, a post-flight reflectance map (in a well-known shapefile (SHP) format) of selected crops can be imported into available farm management software for further diagnosis and/or imported directly into a tractor console. However, such analysis is on a post-flight basis.
Therefore, a need exists for an improved technique that utilizes agricultural drones to improve the use, control and effectiveness of agricultural boom sprayers in real-time.